Patents U.S. Pat. Nos. 6,626,909 and 6,669,729, the entire contents of which are expressly incorporated herein by reference describe spine fixation assemblies that utilize plates as connecting and stabilization elements. Plates are secured to vertebral bones via screws. The screws presented in these two patents are capable of pivoting around a fixed axis of the stabilization plates to achieve variable angular positions relative to the plates. This limited range of relative angular positioning is acceptable for many spinal pathologies. However, in some cases it is preferred to have screws that provide multi-axial pivoting relative to the stabilization plates.